The Preparation And Magnetic Properties Of Ni-based Magnetic Films And Nanowires

Ni-based magnetic thin films can be widely used in the magnetichead and magnetic storage devices due to its magnetic anisotropy andcorrosion resistance. In order to increase the storage density without affectingits performance, nanowires were investigated as the research hotspot. Thisarticle focused on the NiCo and NiFe thin films and nanowires by controllingthe deposition potential, the current density, bath temperature and pH value.Effects of different parameters on the structure, composition, morphology andmagnetic properties of the films and nanowires were investigated. This papermainly included the following three aspects:I. Preparation of NiCo magnetic thin filmsElectrochemical methods were used in the growing of brass base and copperbase NiCo magnetic thin film. Influences of current density and depositiontemperature on the film composition, morphology and magnetic propertieswere investigated. With the current density increased, the saturationmagnetization of the films increased firstly and then decreased. When thecurrent density was200A/m2, the film saturation magnetization was max. Thecrystal structure of the film and preferential growth orientation did notchanged with current densities. However, the saturation magnetizationchanges significantly with current densities. The films density increased whenthe surface current density was150A/m2. Samples coercivity was minimal at55℃. Increasing the temperature, the crystal structure did not changed, butcrystallinity and crystal grain size changed.NiCo films were deposited on the copper substrate. With increasingcurrent density, the density of the film surface gradually increased. When thecurrent density was200A/m2, the film density reached to max and intensity ofsubstrate peak decreased. The strengthen of diffraction peaks of NiCo alloy increased. The reason was that with the increasing of the current density, theenergy transfer increased in solution ions to promote the combination of alloyion. The coercivity of NiCo film was the least with14.31Oe under thecondition of200A/m2. The density of the films increased with the increasingof times. When the deposition time was5min, the Co (100),(200) and (311)of peaks were founded. Co (100) and (200) disappeared after the depositiontime increased. While increasing the deposition time, the coercivity of theNiCo film was reduced. The morphology of magnetic thin NiCo films changedwith the temperature. As the temperature increased, the magnetic properties ofthin film changed. When the bath pH is1.5, the particle size of film is large,showing tumor-like structure. However, particle size of films changed withincreasing pH. When the pH was increased to6, the film surface is smooth.pH values could not change diffraction of film plane. The saturationmagnetization of the film is not affected by pH values. Nevertheless, coerciveforce of the film is different with the change of pH values. When the pH is4,the magnetic thin film can be optimal.II. The preparation of NiFe magnetic thin films on Cu substrateEffects of the deposition temperature, current density, and molar ratio onmorphology, structure and magnetic properties of NiFe film were investigated.The results indicated the grain size of NiFe film and the film surface wasimproved by changing the deposition conditions. NiFe films possessed highlycrystalline at60℃with the lowest coercivity (0.18KA/m) and the highestsaturation magnetization. The corrosion of the film had good soft magneticproperties at a current density of167A/m2. When changing the molar ratio, thecorrosion potential of the film gradually increased. This is because, with theconcentration of Ni increased, the Fe content of the film decreased. Thecorrosion of NiFe would gradually approach the corrosion resistance of themetal Ni.III. Ni-based nano-wire Preparation and magnetic studiesDuring the experiment, this paper is mainly about preparation of NiCo andNiFe of the Ni-based nanowire. Morphology and performance were impacted with deposition potential, deposition time and molar ratio.NiCo nanowires prepared under different deposition potential conditionscould be observed with approximately90nm diameter. When the depositionpotential was-1.6V, the nanowires had a relatively good soft magneticproperties. Changing the deposition time, the length of the nanowire increasedand the crystal structure changed. When the deposition time was5h, thepolycrystalline structures of the metal Ni and Co metal possessed the singlecrystal form of solid solution nanowires. Ni (111) diffraction peak hadmaximum peak intensities. After changing the molar ratio of Ni and Conanowires of different contents, the magnetic nanowires can be also changed.The soft magnetic properties of nanowires were optimal at pH of3.5. Withincreasing pH, the nanowires had hysteresis anisotropy.NiFe magnetic nanowires were prepared using electrochemical methods.NiFe nanowires have a minimum coercivity in deposition potential of-1.2V.Under different conditions of deposition potential, the samples have thehysteresis anisotropy. At higher pH values, the saturation magnetization of thesample was reduced while the coercive force increased. At pH of4, thecoercivity of nanowires was minimum with optimum soft magnetic properties.Template prepared using different aperture obtained nanowires with differentdiameters. NiFe nanowire films possessed hysteresis anisotropy.